The principal objective of peptide-based immunotherapy in IDDM is to arrest human islet destruction by modulating the immunologic balance towards down-regulation of aggressive autoimmunity. This approach will require selection of the appropriate peptides, optimization for in vivo use, appropriate choices of adjuvants and route of immunization and finally, human safety and efficacy trials. The objective of this project is to achieve the first two of these steps on the path to realizing the goal of human peptide immunotherapy for diabetes. We will identify the peptides from autoantigens suitable for recognition in diabetic and genetically at-risk individuals and we will determine whether the recognition of these peptides is likely to yield regulatory, immune- modulatory therapeutic outcome. We will analyze T cell responses to GAD65, pre pro-insulin, and IA-2 to identify immunodominant peptides presented to human CD4+ T cells in the context of HLA-DRB1*0401, *0402, *0404, *0405, *0301, and DQB1*302 and *201. After determining a "short list" of key peptide-class II pairings, we will determine characteristic cytokine responses following T cell activation and analyze genetic and cellular variation which contributes to differential antigen processing and presentation. Detailed peptide binding studies will be used to modulate both MHC allelic specificity and optimize and/or modulate TCR recognition using substituted peptides for key epitope-class II pairings. In close collaboration with the other projects in this program, this project will bridge the gap between identification of potential autoantigen epitopes in the transgenic mouse studies and future peptide based immunotherapy in humans.